The invention relates to an apparatus for producing ozone, wherein air or oxygen is passed through two high voltage electrodes located opposite each other in a housing and is converted into ozone by electrical discharge.
Apparatus for producing ozone are known. The oxygen molecule may be split by supplying thermal energy. However, this method produces only a low ozone yield, since elevated temperature simultaneously promotes the endothermic decomposition of the ozone. Thus, even at 2000.degree. C only about 1% by volume of ozone is in oxygen equilibrium, of which only about 1/10 % remains on rapid cooling, since the endothermic overall decomposition of the ozone continues as the temperature falls.
Therefore, it is more appropriate to produce the oxygen atoms at a low temperature by supplying electrical, optical or chemical energy and then allow them to react further, since at low temperatures the decomposition equilibrium is only created extremely slowly in the absence of catalysts, with the result that the ozone once formed is retained as a metastable compound. The supply of electrical energy may take place, for example, in a so-called "Siemens Ozoniser," which consists fundamentally of two glass tubes placed one inside the other, the outer or inner wall of which is water cooled and connected conductively to the ends of an induction coil. In the narrow annular space between the glass tubes, electrical discharges occur when voltage is applied, through which a dry oxygen or air current is passed. The mixture leaving the ozonizer has a 15% ozone content at best.
The possible range of uses for ozone has therefore not hitherto been used to the full, because the costs of ozone production are too high. Present-day methods of manufacturing ozone require too much expensive energy, and with the known ozonizers only 5 to 15% of the electrical energy is used for producing ozone, whilst the remaining energy is converted into heat.
The best known method of producing ozone up till now is that of electrical discharge in air or oxygen. This discharge takes place in the gap between two insulated electrodes to which an alternating current is applied. In the first period, positive ions accumulate on the surface of one electrode and negative ions on the opposite insulator, these then being discharged in the second period. These ozonizers known at present cannot be operated with direct current, since direct current cannot pass through the insulators. DC ozonizers are indeed also known, but have hitherto been of importance only for scientific purposes. They have not been used industrially, although it was plain that DC corona ozonizers are simpler and more economical to construct and operate.
An improvement on this is provided by an ozonizer according to U.S. Pat. No. 3,842,286 which already ensures a substantial increase in the ozone yield, but in order to produce the corona it requires two electrical fields, a high voltage of about 60,000 volts with correspondingly high demands on the construction material and, finally, a dryer for the gaseous medium which is to be reacted must be provided, since the ozone yield decreases appreciably as the moisture level increases.